1. Field of the Invention
The invention relates to an electrical terminal block, especially for locking onto a mounting rail. The invention particularly relates to electrical terminal blocks having a plurality of base terminals located next to one another and a plurality of connectors located next to one another and mounted on the base terminals.
2. Description of Related Art
Electrical series terminals have been known for decades and are being used in the millions in the wiring of electrical systems and devices. Series terminals are generally locked onto mounting rails that are often located in multiples in a control cabinet. The series terminals are generally made as connecting terminals so that they have at least two conductor terminal elements that are electrically connected to one another via an electrically conductive connecting bar, known as the conductor bar. In addition to this basic type of series terminals, there are many different types of series terminals that are especially adapted to the particular applications. Examples of the different types are two-tier or three-tier terminals and three-wire or four-wire terminals, which then each have a correspondingly larger number of conductor terminal elements.
In addition, there are also electrical series terminals in which at least one conductor terminal element is replaced by a receptacle. In that case, a connector having a corresponding plug-in contact can be plugged onto this receptacle. The conductor terminal element for connecting the electrical conductor is located in the housing of the connector.
Such an electrical series terminal is known from German Utility Model DE 295 14 711 U1. In this disclosure, the base terminal is generally locked onto a mounting rail so that the base terminal represents the stationary part of the electrical series terminal. Conversely, the connector forms the movable part of the electrical series terminal, since it can be easily plugged onto and pulled off of the corresponding receptacles of the base terminal by means of its plug-in contact. While the electrical supply lines are connected to the base terminal or to the conductor terminal elements located in the base terminal, the electric lines of the individual consumers are connected to the conductor terminal elements in the connector.
Since electrical series terminals are generally made disk-shaped, they are assembled generally with several other electrical series terminals to form a terminal block. In these known electrical series terminals, it is then possible to reduce wiring work and also installation efforts by connecting the electrical conductors of individual consumers to a corresponding number of connectors. Then, the connectors that can be combined into a connector block need to simply be inserted into a base terminal block, the base terminal block having been assembled from the corresponding number of base terminals.
Conductor terminal elements in series terminals are largely screw terminals or spring force terminals, especially tension spring terminals. The clamping principle in tension spring terminals is similar to that of screw technology. While in the screw terminal a tension sleeve pulls the conductor against the conductor bar by actuating a terminal screw, in a tension spring terminal this task is performed by the tension spring. To do this, the pretensioned tension spring is opened with an actuating tool, for example a screw driver, so that the conductor can be inserted through a window in the spring leg of the tension spring into the terminal space. After removing the actuating tool, the conductor is pulled by the spring force of the tension spring against the conductor bar.
Both in the screw terminal and in the tension spring terminal, the electrical conductor must first be stripped after it is cut to length before the electrical conductor can make contact. Since a special tool is necessary for stripping the electrical conductor, and since stripping is relatively time-consuming, for many years electrical terminals have also been used to which electrical conductors can be connected without prior stripping. To do this, the insulated conductor is inserted into a conductor receiver in the housing of the terminal and then pressed into an insulation piercing element, by which the insulation of the conductor is cut through and contact is made with the core of the conductor by the insulation piercing elements.
For reliable mechanical connection of connectors and the base terminal, in the electrical series terminal known from German Utility Model DE 295 14 711 U1, there is a fixing element that is fixed to the front of the connector and extends behind the housing projection on the front of the base terminal. In known electrical series terminals, the base terminal has two receptacles, but the connector can only be plugged into the outer of the two receptacles, since otherwise the connector can no longer be fixed on the base terminal with the fixing element.
German Patent Application DE 100 45 498 A1, which corresponds to U.S. Pat. No. 6,506,071, likewise discloses an electrical series terminal with a base terminal and two connectors. In this series terminal in the terminal housing of the base terminal between the two receptacles, a locking element is formed so that the connector at both receptacles can be mechanically connected to the terminal housing of the base terminal. Forming a locking element in the base terminal thus obviates the necessity of placing the connector on the outer receptacle, so that the fixing element can be locked laterally on the connector housing of the base terminal.
In the electrical series terminal described above, however, a separate fixing element is necessary that connects the connector on the front to the base terminal. If the fixing element is lost, it is possible that a connector can be unintentionally pulled out of the base terminal. This is especially true when several connectors are to be combined into a connector block, and a plurality of fixing elements are necessary to ensure reliable and permanent mechanical fixing of the connectors on the base terminals.